Rotary hammer



H. 0. SHORT ROTARY HAMMER Feb. 23, 1965 4 Sheets-Sheet 1 Filed July 30, 1962 HAROLD 0. SHORT H. 0. SHORT ROTARY HAMMER Feb. 23, 1965 4 Sheets-Sheet 3 Filed July 30, 1962 HAROLD 0. SHORT ATTORNEY Feb. 23, 1965 H. 0. SHORT 3,170,523

ROTARY HAMMER Filed July so, 1962 4 Sheets-Sheet 4 FIG. I3

L MMERING & 'ON) V H! I ATTORN United States Patent 3,170,523 ROTARY HAMMER Harold 0. Short, Towson, Md., assignor to The Black and Decker Manufacturing Company, Towson, Md., a corporation of Maryland Filed July 30, 1962, Ser. No. 213,363 11 Claims. (Cl. 173-104) The present invention relates to a rotary hammer of the type having an impacting ram, and more particularly, to a hammer which is capable of selectively rotating a tool bit simultaneously with a percussive driving of the tool by the ram, so as to result in either hammering plus rotation, hammering only, or rotation only.

State of the art In the prior art, of which I am aware, various types and designs of rotary hammers have been illustrated. For example, some utilize a flexible shaft to form a rotative coupling between the motor and a collar or nose piece which is secured onto the shank of the tool. Others have a longitudinal shaft with a pinion formed on the end of the shaft, so as to engage a gear or member which is suitably coupled to the shank of the tool bit; the shaft may then be rotated either by poweroperated means or by a hand wheel. Still others feature a ratchet wheel that is actuated by a helical pinion, in combination with a pawl, such that the reciprocation of the impacting ram is translated into an inching movement of the tool. Moreover, still others tend to rotate the longitudinal barrel within which the impacting ram is reciprocating; and means are provided therein to couple the forward end of the barrel to the shank of the tool, thereby imparting both a selective rotation and a percussive driving of the tool.

All of these aforementioned designs, however, have certain inherent defects, among which are the following: (1) they tend to be bulky, complicated, cumbersome, unwieldly to operate and costly to manufacture; (2) they tend to break down after repeated usage and do not render trouble-free performance for extended periods of time; (3) they do not provide the high drilling rates desirable in demolition work and in modern construction; and (4) they develop a high torque reaction upon the operator, and upon the rotary hammer itself, whenever the rotating tool becomes stalled or em bedded in the work material, a condition which is espe cially pronounced in drilling relatively-deep holes.

Objects of the present invention Accordingly, it is an object of the present invention to alleviate all of the aforementioned deficiencies by providing a rotary hammer which is compact, easy to operate, relatively inexpensive to manufacture, and yet capable of rendering reliable long-life usage, and which, in comparison to commercially competitive units, provides much faster drilling rates.

It is another object of the present invention to provide a rotary hammer which includes a friction-operated slip coupling in the rotational drive mechanism, whereby the rotation being imparted to the tool is interrupted whenever the rotating tool becomes stalled or embedded in the work material, thereby providing a safety feature to guarantee against injury to the operator or damage to the rotary hammer.

It is yet another object of the present invention to provide a frictionoperated safety slip coupling, which is adjustable for various levels of potential torque reaction, as well as compensatable for wearing of the coupling parts during the extended life of the rotary hammer.

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It is yet still another object of the present invention to provide, in a rotary hammer, a gear journaled for rotation forwardly of the ram, in combination with means forming a socket within the gear, so that by proper selection of the tool, and more particularly the shank portion thereof, the rotary hammer can be made to deliver either a hammering plus rotation, or a hammering only, or a rotation only of the tool.

It is a further object of the present invention to provide a rotary hammer which includes a longitudinal barrel detachably secured to the gear case of the hammer and extending forwardly therefrom substantially perpendicular with respect to the motor housing, in combination with an auxiliary housing, which is also detachably secured to the gear case, and which extends forwardly therefrom below the barrel and substantially parallel With respect to the barrel, thereby allowing the rotary hammer to be quickly and easily disassembled for rapid and efficient service.

General description of the present invention In a preferred embodiment, constructed in accordance with the teachings of the present invention, there is provided a rotary hammer having a housing which includes a barrel, an impacting ram floating within the barrel, and power-operated means to reciprocate the ram. An auxiliary housing, which may take the convenient form of a tube or sleeve, is detachably secured to the housing, below the barrel, and extends substantially parallel to the barrel. A shaft is journaled for rotation within the auxiliary housing, and power-operated means are provided to rotate the shaft. A pinion is loosely mounted upon the forward end of the shaft, and an adjustable friction-operated slip coupling is provided to couple the pinion to the shaft. A gear is journaled for rotation in the housing, forwardly of the impacting ram, and is adapted to mesh with the pinion on the rotating shaft; and a non-circular socket is formed in the gear for receiving the shank of a tool therein. Consequently, the tool may be rotated by the gear and simultaneously driven by the percussive force exerted by the impacting ram; or else, by proper selection of the tool, and more particularly its shank, either a pure rotation or a pure hammering may be obtained. In the rotative condition, either with or without hammering, should the tool thereafter become embedded in the work and resist a further turning thereof, then the slip coupling automatically disengages the rotative drive to the pinion; and hence the gear, which is constantly in mesh with the pinion, is no longer being rotatively driven, thereby precluding any undue torque reactions upon either the operator or upon the rotary hammer.

General description of the drawings These and other objects of the present invention will become apparent from the reading of the following specification, taken in conjunction with the enclosed drawings, in which:

FIGURE 1 is a side elevational view of the complete rotary hammer;

FIGURE 2 is an enlarged longitudinal section of the rotary hammer shown in FIGURE 1;

FIGURE 3 is a view taken along the lines of 33 of FIGURE 2, showing a front elevation of the nose housing of the rotary hammer;

FIGURE 4 is a sectional view taken along the lines 44 of FIGURE 2, showing in detail the longitudinal barrel and the auxiliary housing within which the shaft is journaled for rotation;

FIGURE 5 is a stepped section view, taken along the lines 55 of FIGURE 2-, and showing in detail, the

means for detachably securing the barrel and the auxiliary housing to the gear case;

FIGURE 6 is a sectional view taken along the lines 66 of FIGURE 5, and further illustrating the means for detachably securing the'auxiliary housing to the gear case;

FIGURE 7 is a section view taken along the lines 77 of FIGURE 4;

FIGURE 8 is an elevational view, partly in section, showing the rotating gear and meshing pinion as illustrated in FIGURE 2, but with the nose housing removed from the barrel of the rotary hammer;

FIGURE 9 is an exploded elevational view of the adjustable friction-operated slip coupling means included in the rotative drive mechanism;

FIGURE 10 is an exploded elevational view of the complete rotary harrnner, with parts broken away and sectioned, to illustrate the barrel removed from the gear case, and to further illustrate a preferred means for adjusting the friction-operated slip coupling;

FIGURE 11 is a slightly-enlarged detailed section view taken along the lines 1111 of FIGURE 10;

FIGURE 12 is an exploded perspective view showing the barrel and the auxiliary housing removed from the gear case, and further showing the nose housing removed from the barrel;

FIGURE 13 is a view corresponding to a portion of FIGURE 2, but illustrating a tool inserted in the rotary hammer to provide a combination of both hammering and rotation;

FIGURE 14 is a section view taken along the lines 14 14 of FIGURE 13;

FIGURE 15 is a view corresponding substantially to FIGURE 13, but showing a different tool inserted in the rotary hammer so as to provide a hammering action only with no rotation being imparted to the tool;

FIGURE 16 is a section View taken along the lines 16 16 of FIGURE 15;

FIGURE 17 is a view corresponding substantially to that of FIGURES 13 and 14, but showing a still different tool inserted in the rotary hammer so as to provide a rotation only with no hammering being imparted to the tool; and

FIGURE 18 is a detailed section view taken along the lines 1818 of FIGURE 17.

General structure of the rotary hammer With reference to FIGURES 1, 2, 3, and 5, and to FIG- URES 10 and 12, there is illustrated a rotary hammer 1t), constructed in accordance with the teachings of the pres ent invention, and including a motor housing 11, a gear case 12 and a gear case cover 12a secured on top of the motor housing 11, an end handle 13 which includes a finger-actuated trigger switch 14, a conventional electric cord 15, a longitudinal barrel 16, an auxiliary housing 17, a nose housing comprising a barrel end cover 18- and a nose piece 19, and a retainer 26 to maintain a suitable tool within the rotary hammer It The gear case 12 and gear case cover 12a are secured to the motor housing 11 by means of a plurality of screws and lugs 21; and the barrel 16 is detachably secured to the gear case 12 by means of the screws 22. Moreover, the barrel endv cover 18 is secured to the respective forward end of the barrel 16 by means of the screws 23, while thernose piece 19 is detachably secured to the barrel end cover 18 by means of the screws 24.

The auxiliary housing for the rotating shaft With reference again to FIGURES 1, 2, and 5, and with further reference to FIGURES 6 and 7, the auxiliary housing 17 preferably comprises a tube or sleeve having a pair of external annular grooves 25 and 26 formed thereon. The forward lower end of the barrel 16 is provided with a threaded boss 27, radially and perpendicularly of the external annular groove 25; and the gear case 12, as shown 4 i more particularly in FIGURES 5 and 6, is provided with a threaded boss 28, radially of its corresponding external annular groove 26, skewed with respect to the groove 26, and directed inwardly towards the gear case 12 as is shown in FIGURE 6. A set screw 27a is received within the threaded boss 27, while a set screw 28a is received within the threaded boss 28, thereby detachably securing the sleeve 18 to the barrel 16 and to the gear case.12, respectively.

The percussive drive mechanism of the rotary hammer With reference again to FIGURE 2, the motor housing 11 includes a conventional electric motor, which is not shown for ease of illustration, but which, preferably, is of the universal type and has a pair of electrical brushes engaging a commutator. One of the brushes is shown generally by the broken lines, as at 29, and a brush holder retaining ring 30 is detachably secured to the motor hous ing 11 by means of the screws 31; The motor includes an armature shaft 32 journaled in a ball bearing 33, the latter being retained within the gear case cover 12a; and a fan 34 and fan hub 35 are mounted upon the armature shaft 32 adjacent to one side of the bearing 33. A pinion 36 is formed on the end of the armature shaft 32 which protrudes within the gear case 12. A crankshaft 37 is journaled in the gear case 12 by means of a ball bearing 38, which is held within the gear case 12 by means of a retaining ring 39 and screw 39a. The opposite end of the crankshaft 37 is journaled within a sleeve bearing 40, which is press-fitted within the bore 41 formed in the gear case cover 12a. The crankshaft 37 carries a gear 42 which engages the pinion 36. A second pinion 43 is formed on the crankshaft 37 between the gear 42 and the sleeve bearing 40. A stub shaft 44 is journaled within sleeve bearings 45 and 46 in the gear case 12, and the sleeve bearings 45 and 4-6 are received within the respective bosses 47 and 48 formed in the gear case 12 and gear case cover 12a, respectively. The stub shaft 44, as well as the crankshaft 37, have respective axes which are parallel to the armature shaft 32; and the stub shaft 44, as shown more particularly in FIGURE 2, is on the side of the crankshaft 37 which is opposite from the armature shaft 32. The stub shaft 44 has a collar or shoulder 49 formed thereon, and a thrust Washer 59 is interposed between the shoulder 49 and the gear case cover 12a. Also, an oil plug 51 is provided for the sleeve bearing 46, while a similar plug 51a is provided for bearing 40. The stub shaft 44 has a bevel gear 52 pressed thereon; and bevel gear 52 is nested within a pressfitted gear 53, which engages the pinion 43 which is formed on the crankshaft 37. The crankshaft 37 has a crank pin 54; and a connecting rod 55 is mounted upon the crank pin 54, a needle bearing 56 being interposed therebetween. The opposite end of the connecting rod 55 engages a wrist pin 57, which is received within a crosshead 58. The cross-head 58 is guided within the bore 59 0f the barrel 16. A tubular pistonrod 60 is formed integrally with the cross-head 58, and a piston 61 is formed on the opposite end of the piston rod 6% A floating ram 62 is guided for reciprocation within the barrel by means of rails 63, which are formed on the ram 62. Preferably, but not necessarily, the piston 61 is telescopically received within the ram 62, and ram 62 is preferably formed as a hollow cylindrical member having a closed forward end. Consequently, a chamber 64 is formed between the piston 61 and the ram 62, and a cushion of air is entrapped in the chamber 64.

The entrapped air in the chamber 64 exhibits alternate compression and suction effects so as to alternately advance and retract the ram 62,'respectively, as the piston 61, is reciprocated within the barrel 16 by means of the connecting rod 55 and the crankshaft 37. Momentary venting means are then provided for the entrapped air in chamber 64, so that the mass of air in the chamber 64 may vent at certain times during the operating cycle of the mechanism, thereby adjusting to a substantially constant working level. This momentary venting means may take the convenient form which includes an internal annular recess 65 formed within the ram 62, whereby the axial length of the internal annular recess 65 is greater than the axial height of the relatively-short disc-shaped piston 61; and consequently, the entrapped air in the chamber 64 may vent to atmosphere whenever the piston 61 passes by the recess 65, it being appreciated that the piston 61 and ram 62 will ordinarily reciprocate relatively, that is to say, out of phase with each other. Such momentary venting means are described more particularly in the Akerman Patent 3,034,302, issued on May 15, 1962, entitled Momentary Venting Means for Power- Operated Percussive Tool, and assigned to the same assignee as that of the present invention. However, it will be appreciated that the present invention is equally applicable to all forms of power-operated percussive drive mechanisms, and that the particular form of percussive drive mechanism, herein illustrated for convenience of illustration, is not to be construed as limiting the essence of the present invention.

Moreover, the piston 61 may carry a protrusion 66, while the closed forward end of the ram 62 may have a cooperating recess 67. At certain times over the life of the mechanism, as when the sealing ring 68 (carried by the piston 61) wears away or becomes ineffective, the entrapped air in the chamber 64 may be reduced to such an extent that a bottoming or impacting between the ram 62 and the piston 61 may occur; and in order to prevent the continued impacting of the piston 61 against the closed forward end of the ram 62, the protusion 66 is adapted to be received Within the recess 67. Thereafter, the ram 62 is coupled to the piston 61 for rotation in unison, and any further impacting or bottoming etween the piston 61 and the ram 62 is precluded.

Such a structure is described more particularly in the Atkinson Patent 3,032,998, issued on May 8, 1962, entitled Ram Catcher for Piston-Ram Assembly, and assigned to the same assignee as that of the present invention. However, it will be further appreciated that the present invention may be utilized, equally as well, with or without such ram catcher means.

The rotative drive mechanism and the slip clutch included therein With reference again to FIGURE 2, the auxiliary housing or sleeve 17 is provided with a pair of sleeve bearings 69 and 71) so as to journal the rotating shaft 71. The internal end of the shaft 71 (adjacent to the gear case 12) has a bevel pinion 72 formed thereon, and a thrust washer 73 is interposed between the pinion 72 and the sleeve 17. The pinion 72 meshes with the bevel gear 52 carried by the stub shaft 44, thereby imparting rotation to the shaft 71.

With reference again to FIGURE 2, and with further reference to FIGURES 8 and 9, the opposite end of the shaft 71 is provided with a shoulder 74, while the-extreme end of the shaft 71 is threaded as at 75. A pinion 76, having a sleeve bearing 77 pressed therein, is loosely mounted upon the shaft 71. A shoulder washer 78, a key washer 79, and a thrust washer 86 are interposed between one end of the pinion 76 and the shoulder 74 formed on the shaft 71. On the opposite side, of the pinion 76, a thrust washer 81, a key washer 82, and a plurality of cone-type of lock washers 83 are carried by the shaft 71; and a clamp nut 84 engages the threaded end 75 of the shaft 71. Hence, a friction-operated slip coupling is provided to rotatively couple the pinion 76 to the shaft 71.

The rotating gear With reference again to FIGURE 2, the extreme forward end of the barrel 16 has a sleeve nut 85 threadably received therein, and an G-ring 86 and beat piece 87 are interposed between the sleeve nut 85 and a split collet 88. The sleeve nut 85 has a flange 89, and a spring washwhatsoever.

er 99 is interposed between the flange 89 and the barrel 16. A sleeve bearing 91 is press-fitted within the sleeve nut 85, while a bushing 92 is press-fitted within a bore 93 formed in the barrel end cover 18. A gear 94 is journaled within the barrel end cover 18 by means of the sleeve bearing 91 and the bushing 92, while a washer 95 is interposed between the gear 94 and the sleeve bearing 91. The gear 94 has an integral forwardly-extending sleeve 96, which is journaled within the bushing 92; and a closure or seal 92a is provided between the bushing 92 and the nose piece 19. Moreover, the gear 94 further has a rearwardly-projecting integral sleeve 97 which is journaled within the sleeve bearing 91. As shown shown in FIGURES 2 and 8, the gear 94 meshes with the pinion 76 which is loosely mounted upon the rotating shaft 71. The gear 94 is formed with an axial bore 953, while the forward integral sleeve 96 of the gear 94 is formed with a communicating axial counterbore 99. Also, the rearward integral sleeve 97 of the gear 94 is formed with a non-circular or hexagonal socket 159, which communicates with the bore 98 and the counterbore 99, and the purpose of the socket 190 will hereinafter be described in detail.

Selection of the desired force to be applied to the tool With reference to FIGURES 13 and 14, a tool 101 has been inserted within the rotary hammer 10. The tool 191 is adapted for both hammering plus rotation. It has a shank portion 162 which is adapted to be received within the counterbore 99, a shank portion 103 (of reduced diameter) which is adapted to be received within the bore 98, and finally, a hexagonal shank portion 164 which is adapted to be received within the socket 199 of the gear 94. The length of the hexagonal shank 194 is such that it protrudes within the barrel 16 radially adjacent to the split collet 88, so that the tool 101 will be engaged and impacted against by the floating ram 62. Simultaneously, the rotation of the shaft 71 and pinion 76 is transmitted to the gear 94, so that the gear 94 rotates within the nose piece 19. Consequently, the tool 191, which has a rotative coupling to the gear 94 by means of the hexagonal shank 194 and the socket 160, will itself rotate; and the result is such as to achieve both hammering plus rotation.

With reference to FEGURES 15 and 16, a different tool 195 has been inserted within the rotary hammer 19. This tool 195 has a round shank 166 adapted to be received within the counterbore 99, a round shank 107 (of reduced diameter) which is adapted to be received within the bore 93, and another round shank 1118 (of still further reduced diameter) which is loosely engaged within the socket 191 of the gear 94. The length of the shank portion 163 of the tool 165 is substantially the same as the length of the hexagonal shank 194 of the tool 101, so that the tool 195 is impacted against by the ram 62. However, because the shank 198 is round, it will not have a keyed or rotative coupling with the socket so that even though the gear 94 is rotating, no rotation will be transmitted to the tool 105. Consequently, the mechanism now provides a pure hammering or percussive force to the tool 195 with no rotation whatsoever. Indeed, to guard against any rotation of the tool 105, should there ever be a frictional engagement between the round shank 168 and the socket 1610, the tool is further provided with a non-circular portion 109, preferably hexagonal, which engages within the hexagonal socket 111? formed on the nose piece 19. The nose piece 19 is rigid or stationary, and consequently, the tool cannot rotate within the rotary hammer 10.

With reference to FIGURES 17 and 18, a still diiferent tool 111 has been inserted in the hammer 10 so as to provide pure rotation without any impacting or hammering The tool 111 has a round shank portion 112 received within the counterbore 99, a round shank portion 113 (of reduced diameter) adapted to be received within the bore 98 of the gear 94, and a hexagonal shank portion 114 adapted to be received within the socket 161) of the gear 94. However, the hexagonal portion 114 of the tool 111 is of a shorter length, than that which is shown in FIGURES 13 or 15, such that the tool 111 does not protrude sufiiciently within the barrel 15 to enable the ram 62 to impact against theend of its hexagonal shank portion 114; and as shown in FIGURE 17, the ram 62 will be driven down and will be held by the split collet 88 as the piston 61 is still being reciprocated through the crankshaft 37 andthe connecting rod 55. With this tool 111, pure rotation is obtained without any hammering whatsoever.

With reference to FIGURE 18, it is shown that the spring retainer which is used with all the tools (161, 105, and 111) is retained on the nose piece 19, see FIG- URE l, and has an annular portion 115 which is adapted to be engaged by the collar 116 formed on each of the tools 101, 105, and 111, thereby preventing these tools from being driven out of the rotary hammer 19. This is of course a safety precaution and is prevalent in the art relating to power-operated hammers.

The tool 191, which is selected to obtain both a hammering plus a rotation from the rotary hammer 16, is provided with a carbide insert 117 as well as a conventional spiral flute 113 as is shown in FIGURE 13. The tool 105, which is selected to obtain a pure hammering from the rotary hammer 11), has a bullpoint 119 as is 1 shown at FIGURE 15; but it will be appreciated that other types of tools, such as a fiat chisel, may be utilized. Finally, the tool 111, which is selected to obtain a pure rotation from the rotary hammer 10, has a spiral cutting flute 120.

Adjustment of the slip coupling means Consequently, it will be appreciated that a rotary hammer is provided which is rugged and reliable, which is relatively inexpensive to manufacture, and which may be quickly disassembled for rapid servicing. Moreover, the rotative drive mechanism includes a friction-operated slip coupling, which protects both the operator and the rotary hammer from undue torque reactions should the tool become locked-up or embedded in the work material; and this slip coupling is adjustable, quickly and easily, for various predetermined levels of torque release. Furthermore, the rotative drive mechanism includes a gear which is journaled for rotation forwardly of the impacting ram, and means are provided within the gear so that the type of desired force or action to be applied to the tool may be pre-selected by means of the particular tool, and more specifically, the shank of the tool that is inserted within the rotary hammer. Consequently, either pure rotation, or pure hammering, or a combination of both hammering and rotation may be obtained. The rotary hammer of the present invention further provides faster drilling rates than that which is presently obtainable from competitive units on the commercial market. For example, in the rotation plus hammering position, and drilling into a block of concrete, a one inch diameter hole, approximately seven inches deep, may be drilled in approximately one minute, a drilling rate superior to that which is previously available. Yet the rotary hammer of the present invention is both safe and easy to operate.

Obviously, many modifications may be made without departing from the basic spirit of the present invention; and accordingly, within the scope of the appended 81 claims, the invention may be practiced other than has been specifically described.

I claim:

1. A rotary hammer for driving a tool, comprising:

(a) a motor housing;

(1;) a gear case secured on top of said motor housing;

(c) a motor in said motor honsing;

(d) said motor having an armature shaft protruding within said gear case; Q

(e) a longitudinal barrel detachably secured to said gear case and projecting forwardly therefrom substantially perpendicular to said motor housing;

(i) an auxiliary housing comprising a sleeve detachably secured to said gear case and projecting forwardly therefrom to one side ofand substantially parallel to said barrel;

(g) a piston reciprocating in said barrel;

(h) a ram floating in said barrel forwardly of said piston and driven by said piston;

(i) crank means interconnecting said piston and said armature shaft;

(j) a shaft journaled in spaced bearings in said sleeve and projecting forwardly therefrom;

(k) gearing means interconnecting said shaft and said armature shaft;

(1) said barrel having a forward end formed with a radial boss, and said sleeve having a respective forward end secured within said boss;

(m) a nose housing detachably secured on said respective forward end of said barrel and enclosing said barrel and said sleeve;

(n) a gear journaled in said nose housing forwardly of said ram;

(0) a pinion loosely carried by said shaft and meshing with said gear;

(p) an adjustable friction slip coupling between said pinion and said shaft; and

(q) said gear having socket means formed therein to receive the shank of the tool, whereby the tool may be rotated by said gear and simultaneously driven by the impacting of said ram.

2. A rotary hammer as described in claim 1, wherein:

(a) said nose housing comprises a barrel end cover secured on said respective forward end of said barrel; and

(b) a nose piece secured forwardly of said barrel end cover.

3. A rotary hammer as described in claim 2, wherein:

(a) said gear has a first integral sleeve extending forwardly therefrom and further has a second integral sleeve projecting rearwardly therefrom; and wherein:

(b) said first integral sleeve is journaled in said barrel end cover; and v (c) said second integral sleeve is journaled in said respective forward end of said barrel.

4. A rotary hammer as described in claim 3, wherein:

(a) said gear has an axial bore formed therein;

(b) said first integral sleeve of said gear has an axial counterbore formed therein; and

(c) said second integral sleeve of said gear has a hexagonal socket formed therein;

(0) said bore, said counterbore, and said socket communicating with each other, whereby the shank of the tool determines the type of driving force imparted to the tool.

5. A rotary hammer as described in claim 1, wherein:

(a) said sleeve has first and second external annular grooves formed thereon, one .each'spaced from a respective end of said sleeve;

(b) a boss formed in said nose housing radially and perpendicularly of said first external annular groove;

(c) a boss formed in said gear case radially of said second external annular groove;

(d) said last-named boss being skewed with respect to the axis of said sleeve and being directed inwardly towards said gear case; and

(e) respective fastening members received within each of said threaded bosses to seat within said respective external annular grooves in said sleeve, whereby said sleeve is detachably secured to said gear case and said nose housing.

6. A rotary hammer as described in claim 1, wherein said adjustable friction slip coupling comprises:

(a) a shoulder formed on said shaft adjacent said pinion;

(b) thrust washer means interposed between said shoulder and said pinion;

(c) a plurality of friction lock washers, stacked one alongside of another, on the side of said pinion opposite from said shoulder;

(d) a threaded end formed on said shaft adjacent said friction lock washers;

(e) a clamping nut received on said threaded end and bearing against said lock washers. thereby frictionally locking said pinion to said shaft; and

(f) means to hold the shaft steady and to simultaneously adjust the degree of frictional engagement of said lock washers, whereby the coupling of said pinion to said shaft is adjustable, and whereby said slip coupling may release whenever the torque upon said gear and pinion becomes greater than a predetermined setting.

7. A rotary hammer as described in claim 6, wherein,

said means to hold the shaft steady comprises:

(a) a hexagonal socket formed within the end of said shaft opposite from said threaded end, whereby a wrench may be inserted in said hexagonal socket while the clamping nut is adjusted.

8. A rotary hammer for driving a tool bit, compris- (a) a housing having a barrel extending forwardly therefrom;

(b) a radial boss formed on the end of said barrel;

() an auxiliary housing comprising a sleeve secured at one end to said housing, extending forwardly therefrom parallel to said barrel, and having its other end secured within said radial boss of said barrel;

(d) a ram reciprocating in said barrel;

(e) a nose housing detachably secured on the forward end of said barrel;

(7) a shaft journaled in spaced-apart bearings in said sleeve and extending into said nose housing;

(g) a pinion loosely mounted on the end of said shaft;

(h) a friction slip coupling between said pinion and said shaft; and

(i) a gear rotatably mounted in said nose housing forwardly of said ram and meshing with said pinion;

(i) said gear having socket means formed therein to receive the shank of the tool bit, the end of which extends into said barrel to be struck repeatedly by said ram.

9. In a rotary hammer, the subcombination of:

(a) a gear journaled for rotation in the forward portion of the hammer;

(b) said gear having an integral sleeve extending therefrom;

pinion and shaft.

10. In a rotary hammer, the combination of: (a) a gear journaled for rotation in the hammer; (b) said gear having an integral portion with socket means formed therein to receive the shank of a tool bit;

(0) a shaft journaled for rotation in the hammer to one side of said gear; (d) means to drive said shaft;

(e) a pinion loosely mounted upon said shaft, said pinion engaging said gear; and (f) a friction-type of slip coupling between said pinion and shaft;

(g) said coupling including a pair of friction washers and at least one other washer loosely mounted on said shaft but keyed thereto for rotation in unison.

11. In a rotary hammer, the combination of:

(a) a gear journaled for rotation in the forward portion of the hammer;

(b) said gear having an integrally-formed axiallyextending portion with a socket formed therein for receiving the shank of a tool bit;

(0) driving means for said gear; said driving means including:

(1) a shaft journaled for rotation in the hammer to one side of said gear, the axis of said shaft being parallel to the axis of said gear; and

(2) a pinion mounted upon said shaft and engaging said gear; and

(d) a friction slip coupling in said driving means;

(e) said slip coupling including (1) resilient mean; and

(2) means engaging said resilient means to vary the point of torque release, whereby said slip coupling is adjustable.

References Cited by the Examiner UNITED STATES PATENTS BROUGHTON G. DURHAM, Primary Examiner. 

11. IN A ROTARY HAMMER, THE COMBINATION OF: (A) A GEAR JOURNALED FOR ROTATION IN THE FORWARD PORTION OF THE HAMMER; (B) SAID GEAR HAVING AN INTEGRALLY-FORMED AXIALLYEXTENDING PORTION WITH A SOCKET FORMED THEREIN FOR RECEIVING THE SHANK OF A TOOL BIT; (C) DRIVING MEANS FOR SAID GEAR; SAID DRIVING MEANS INCLUDING: (1) A SHAFT JOURNALED FOR ROTATION IN THE HAMMER TO ONE SIDE OF SAID GEAR, THE AXIS OF SAID SHAFT BEING PARALLEL TO THE AXIS OF SAID GEAR; AND (2) A PINION MOUNTED UPON SAID SHAFT AND ENGAGING SAID GEAR; AND (D) A FRICTION SLIP COUPLING IN SAID DRIVING MEANS; (E) SAID SLIP COUPLING INCLUDING (1) RESILIENT MEANS; AND (2) MEANS ENGAGING SAID RESILIENT MEANS TO VARY THE POINT OF TORQUE RELEASE, WHEREBY SAID SLIP COUPLING IS ADJUSTABLE. 